LONDON — Seven people were arrested in the UK early Tuesday on suspicion of financing terrorism overseas by illegally exporting the stimulant khat to the US and Canada, Scotland Yard said.

The unnamed suspects were arrested during dawn raids at four homes in London, in the Welsh capital of Cardiff and in Coventry, central England. They were taken to a central London police station for questioning.

The raids were coordinated by the Metropolitan Police’s Counter Terrorism Command — alongside the US Department of Homeland Security — as part of a planned, intelligence-led investigation into illegal exports of khat to North America. Khat is legal in the UK, but a controlled substance in the US and Canada.

Khat is popular in East Africa and the Arabian Peninsula where users chew the leaves then swallow the juice, which contains an ingredient similar to amphetamine. It is also widely used in immigrant African communities across the UK.

The seven suspects arrested Tuesday include six men and one woman. They are aged from 30 years old to 49 years old. Another seven homes and a business were raided, but no arrests were made. Searches were ongoing, Scotland Yard said.